Function Volkswagen Passat B5

Function

Depending on air pressure and ambient temperature, varying quantities of fuel vapors form above the fuel surface in the fuel tank.

The EVAP canister system prevents these HC emissions from entering the atmosphere.

With quantity restrictions, fuel vapors travel from the highest point of the tank via the gravity valve (closed at a tilt of 45 ° ) and the pressure retention valve to the EVAP canister.

The active charcoal stores these gases like a sponge.

While driving, with oxygen sensor control active (engine warm), the Evaporative Emission (EVAP) Canister Purge Regulator Valve N80 , (also called the regeneration valve) is activated by the Engine Control Module (ECM) in pulses dependent on load and engine speed. The opening time is dependent on input signals.

During the cleansing process (regeneration of active charcoal), the intake manifold vacuum sucks fresh air through the air opening on the underside of the EVAP canister. The fuel vapors and fresh air temporarily stored in the active charcoal are added to combustion in doses.

The pressure retention valve prevents fuel vapors from being sucked out of the tank when the Evaporative Emission (EVAP) canister purge regulator valve is opened and an intake manifold vacuum is present. This ensures a complete evacuation of the EVAP canister.

The solenoid valve is closed when no voltage is present (e.g. open circuit in wiring). EVAP canister is not evacuated.

The vacuum line from throttle valve control module to EVAP canister is also connected with crankcase ventilation valve via a bypass. The check-valve integrated there prevents intake air from entering the crankcase in certain partial throttle ranges. This improves overall crankcase venting. The bypass ensures crankcase ventilation.

Note. All hose connections are secured with spring-type clamps or tensioning clamps. Always replace tensioning clamps with spring-type clamps. Hose clip pliers V.A.G 1921 are recommended for installing spring clips.

Observe safety precautions --> Safety precautions when working on fuel supply system

Observe rules of cleanliness --> Rules of cleanliness .

Scheme 184

1 - EVAP canister

1. Component location: in wheelhousing, right front
2. Secured to body
3. To remove, remove right front wheelhousing liner: --> «66 EXTERIOR EQUIPMENT»(ref-255352-S25568548222007053000000)

2 - 10 Nm

3 - Air filter housing

4 - Retaining ring

1. For solenoid valve 1

5 - Evaporative Emission (EVAP) Canister Purge Regulator Valve N80

1. With engine at operating temperature, valve is activated (pulsed) via the Engine Control Module (ECM)
2. Installation position: Arrow points in direction of flow

6 - Connector

1. Black, 2-pin
2. For solenoid valve 1

7 - Throttle valve control module

8 - O-ring

1. Replace if damaged

9 - Vent line

1. Black
2. Check for secure seating
3. From gravity valve at fuel tank

10 - Mounting screw

11 - Breather hose

1. Into the environment
2. Secured to body

12 - To intake hose

1. Between turbocharger and air filter
2. Only on vehicles with turbocharger

13 - Check-valve

1. Gray side to EVAP canister system
2. Only on vehicles with turbocharger

Scheme 185

1. Clamp off LDP outlet (EVAP side) - 1 - using Hose Clamps up to 25 mm dia. 3094 or equivalent.

1. Turn control valve from "Hold" to "Test".
2. Allow fuel system to pressurize.

Note. Fuel system pressurization depends on volume of fuel system and amount of fuel in tank.

If fuel system pressurization does not stabilize

1. Verify that all fuel system outlets have been sealed before continuing.

Note. Any flow shown on flow meter indicates a leak. Flow below flow meter flag set at vehicle leak standard may indicate a sporadic DTC.

If flow meter on tester registers flow near or above pre-set pressure

1. Clamp off hose leading from EVAP canister purge regulator valve N80 to intake manifold.

If flow stops

1. Replace EVAP canister purge regulator valve N80 and repeat test before continuing.

If meter indicates no flow after test

1. Perform quality check and return vehicle to customer.

If flow continues

1. Use smoke generator trigger to charge fuel system with smoke again.
2. Inspect complete EVAP system for escaping smoke.

Note. It may be necessary to move, twist, or wiggle EVAP components around to reproduce leak.

If leak cannot be found using smoke

Scheme 186

1. Locate leak with ultrasonic tester.

1. General search: tester only
2. Localized search: tester with extension wand (left)

If leak cannot be located

1. Disconnect and plug or clamp shut EVAP lines to isolate fuel tank using Hose Clamps up to 25 mm dia. 3094 or equivalent before continuing.

If flow stops

1. Reconnect EVAP lines and search area that was isolated.

When leak has been located

1. Repair leak and repeat EVAP system test.

Note. Because leak may be at top of fuel tank, it may not be possible to locate through fuel pump/sending unit access plate. Lower fuel tank if necessary to locate leak.